1. Field of the Invention
The present invention relates to a compound thin-film magnetic head formed as a laminate of a playback head using a magnetoresistive effect and a recording head using a magneto-inductive effect, and to a method for manufacturing such a compound head, and more particularly to a thin-film compound magnetoresistive effect head in which it is possible to achieve sufficient insulation between magnetic shields.
2. Description of the Related Arts
In the past, compound magnetoresistive effect heads have been widely used in the writing and reading of information with respect to a magnetic recording medium.
Because of a reduction in the relative velocity between the magnetic head and the magnetic recording medium that has accompanied a reduction in size and increase in capacity of magnetic recording media, magnetoresistive effect heads (hereinafter abbreviated MR heads), in which the playback output is not dependent upon the speed, have gained attention in recent years.
MR heads are discussed in xe2x80x9cA Magnetoresistivity Readout Transducer,xe2x80x9d IEEE Trans. on Magnetics MAG-7 (1970), 150.
The most practical MR head, as shown in FIG. 6, is a compound magnetoresistive effect head formed by an MR head having two opposing magnetic shield films S1 and S2, and a magnetoresistive effect (MR) element 8 provided between the magnetic shield films S1 and S2 with intervening magnetic gap layers 3 and 4, i.e., magnetic separation layers made of insulation films, therebetween, and an inductive head (hereinafter abbreviated ID head) formed by one of the magnetic shield S2 of the opposing magnetic shields S1 and S2 as one magnetic pole film P1 and, on a surface of the magnetic pole film P1 opposite from the magnetoresistive effect element 8, a coil 90 held between an insulator and another magnetic pole film P2, these being laminated in parallel with the magnetic pole film P1, magnetic recording being performed by a magnetic field generated in a magnetic gap 95 provided between the magnetic pole films P1 and P2.
FIG. 2 shows a plan view of the above-noted compound magnetoresistive effect head, viewed from the magnetic recording medium surface (air bearing surface; ABS surface).
In an MR head, because the playback track width becomes narrow with an increase in the recording density, a head was disclosed in Japanese Unexamined Patent Publication (KOKAI) No.7-57223, wherein to suppress the side fringe effect a magnetoresistive effect element is disposed only in the playback track part, a ferromagnetic film (hereinafter referred to as a magnetization stabilizer film) for the purpose of stabilizing the magnetization of the magnetoresistive effect element is disposed adjacent to the magnetoresistive effect element.
The above-noted magnetization stabilizer film is used for the purpose of stabilizing the magnetization of the magnetoresistive effect film used as a magnetoresistive effect element in one direction, thickness of this magnetization stabilizer film being determined by the saturation magnetization and thickness of the magnetoresistive effect film.
The dimension of the magnetoresistive effect element in the direction perpendicular to the medium surface (hereinafter referred to as the element height) is made small so as to correspond to the playback track width, and the magnetoresistive effect element is substantially square in shape.
The improvement of recording density is accompanied by a reduction in both the playback track width and the linear recording width.
The linear recording density is dependent upon the spacing between the magnetic shields S1 and S2 (hereinafter referred to as the playback gap).
With a narrowing of the playback gap, there is a reduction of the thickness of the magnetic separation film, which is an insulation film, between the magnetoresistive effect element and the magnetic shields.
In the past, in one method of establishing the element height, ion milling or the like was generally used to perform patterning to an approximate height, after which lapping was performed to establish the final element height.
When the above is done, in performing patterning by ion milling or the like, a step occurs at the etched part.
For this reason, in the past by forming a magnetic separation layer made of an insulation film before forming the magnetic shield S2, this step was covered, thereby preventing an electrical short circuit between the magnetoresistive effect element and the magnetic shield S2.
However, with an increase in the recording density, the magnetic separation layer thickness is decreased, making it difficult to completely cover the step part, so that it is not possible to maintain insulation between the magnetic shield S2 and the magnetoresistive effect element.
The problems accompanying prior art are described below, with reference being made to FIG. 6.
Specifically, FIG. 6 is a cross-section view of a known compound magnetoresistive effect head (MR head) of the seen in the direction of the cutting line Axe2x80x94A shown in FIG. 2 and in the direction of right angle to a paper surface of this FIG. 6.
As one of structures of the magnetoresistive effect element 8 in the above-noted MR head, a surface 50, not in opposition to the recording medium and having a prescribed element height, is established by being patterned with ion milling or the like.
The magnetoresistive effect film (MR film) 5 generally is made of an NiFe film, and a soft magnetic layer is further laminated for applying a vertical bias to the magnetic separation layers G1 and G2 as well as the magnetoresistive effect film 8.
In the case of a spin valve film, the structure is one in which a magnetization fixing layer, a magnetization free layer, and a copper film or the like are laminated.
In either case, the total thickness of the magnetoresistive effect element is approximately 50 nm. By etching the magnetoresistive effect element in the process that performs patterning so as to establish the element height, a step approximately the size of the film thickness of the magnetoresistive effect element is formed.
The resolution of the playback head in the linear density direction is dependent upon the playback gap length, and to achieve high-density recording and playback, it is necessary to make the playback gap length short.
The magnetoresistive effect element 8 is disposed between the lower magnetic shield S1 and the upper magnetic shield S2, and to prevent the current flowing in the magnetoresistive effect element 8 from being divided by the magnetic shields S1 and S2 it is necessary to provide electrical insulation between the magnetic shields S1 and S2.
For this reason, insulation films are provided between the magnetic shield S1 and the magnetoresistive effect element 8 and between the magnetic shield S2 and the magnetoresistive effect element 8.
Note that, a lower magnetic gap G1 is provided between the lower magnetic shield S1 and the magnetoresistive effect element 8, while the upper magnetic gap G2 is provided between the upper magnetic shield S2 and the magnetoresistive effect element 8, so as to serve as insulation films therebetween.
Thus, with an increase in the linear density, the film thickness of these insulation films inevitably becomes smaller.
For this reason, because of the insulation films laminated between the magnetic shields and the magnetoresistive effect element, it is difficult to completely cover the step that is formed by the step of patterning the magnetoresistive effect element so as to establish the prescribed element height, the result being the risk that it will not be possible to maintain the insulation between the magnetic shields and the magnetoresistive effect element.
More specifically, in a conventional MR head as shown in FIG. 6, by restricting one of the heights of the magnetoresistive effect element by performing patterning with ion milling or the like, a step 60 occurs at the edge part of the magnetoresistive effect element, and thus the magnetic gap G2 formed by a film of Al2O3 or the like laminated for the purpose of establishing insulation between the magnetoresistive effect element and the magnetic shield S2 is formed so as to cover this step.
Accompanying an increase in the recording and playback density, however, the spacing between the magnetic shields S1 and S2 (the playback gap) becomes small.
Therefore, the thickness of the magnetic gap layer G2 laminated between the magnetoresistive effect element 8 and the magnetic shield S2 also becomes thin.
The reduction in the thickness of the magnetic gap layer G2 causes a reduction in the magnetic gap G2 covering the step occurring when the magnetoresistive effect element is patterned, thereby worsening the coverage of the step.
As a result, the quality of the insulation between the magnetoresistive effect element 8 and the magnetic shield S2 is worsened, and in an extreme case, an electrical short circuit could occur between the magnetoresistive effect element 8 and the magnetic shield S2.
An example of a method for manufacturing the above-noted compound magnetoresistive effect head of the past is described below, with reference to FIG. 5.
Specifically, FIG. 5(A) is a drawing showing the magnetoresistive effect element 8 and the edge electrode from the same direction as in FIG. 6.
Although not shown in FIG. 5, as can be understood from FIG. 2, the magnetoresistive effect element 8 is formed only in the track part of the MR head, with electrodes being formed so as to be connected to each end thereof.
To form this shape, a magnetoresistive effect film 8 is first grown, after which, as shown in FIG. 5(B), photoresist 16 is formed in a stencil pattern.
Next, as shown in FIG. 5(C), using the photoresist pattern 16 as a mask, etching is done of the magnetoresistive effect film 8 by ion milling, after which a CoCrPt film 11 for application of vertical bias to the magnetoresistive effect film 8 and Au film 12 for the purpose of causing current to flow in the magnetoresistive effect film 8 are sputtered, with the photoresist pattern remaining, after which the photoresist is lifted off.
The magnetoresistive effect film 8 is formed using an RF magnetron sputtering apparatus.
The argon gas pressure when forming the above-noted film is 0.3 Pa, and the RF power is 200 W. Because the photoresist is formed as a stencil, a two-layer resist is used.
The first layer of resist uses a PMGI film that is soluble in an alkaline developer, and the second layer uses a Novolac positive resist.
The accelerating potential used for ion milling of the magnetoresistive effect film 8 is 500 V, and the ion current density is 1.0 mA/cm2.
Sputtering of the CoCrPt film and the Au film was also done using an RF magnetron sputtering apparatus.
FIG. 5(B) shows the formation of the photoresist pattern 16 for establishing one side of the element height, this being formed as a single-layer resist.
FIG. 5(C) is a drawing showing the etching by ion milling, using the photoresist formed as shown in FIG. 5(B), of the magnetoresistive effect film and the CoCrPt film 11 and Au film 12 formed on both ends thereof.
The ion milling in FIG. 5(C) is performed with an accelerating potential of 500 V and a ion current density of 1.0 mA/cm2.
The angle of incidence of the ion beam when performing ion milling is 10 degrees, and the milling time was approximately 5 minutes.
The cross-sectional shape of the wall part 50 of the end parts of the magnetoresistive effect element 8 after etching have a taper angle of approximately 65 degrees.
FIG. 5(D) shows the condition after etching, subsequent removal of the photoresist, and the growth of the upper gap G2 film of Al2O3, and then the formation of the upper magnetic shield S2.
The formation of the upper gap G2 is done using an RF magnetron sputtering apparatus, with an argon gas pressure of 0.077 Pa, an RF power of 2 kW, and an Al2O3 film thickness of 30 nm.
Because flattening was not done in MR heads of the past, the step 60 occurring during etching of the magnetoresistive effect element 8 remained as is.
In this condition, if upper gap G2 of Al2O3 film is formed and then the upper shield S2 is formed, as shown in FIG. 5(D) the distance between the magnetoresistive effect element 8 and the upper shield S2 is reduced at the step part 60.
With the achievement of high linear density in MR heads, with a reduction of the playback gap the thickness of the Al2O3 film forming the upper gap G2 is also reduced, making it very difficult to establish insulation between the magnetoresistive effect element and the upper shield.
In the Japanese Unexamined Patent Publication (KOKAI) No. 9-198624, there is language with regard to the configuration of a compound magnetic head, this disclosure being of the use of a configuration for solving the problem of a step formed in magnetic recording head.
Thus, while there is disclosure of technology for formation of a step-removing layer having a thickness that is the same as the upper shield for the purpose of removing problem of the step of the upper shield, there is no language disclosing technology for solving the problem of a step formed because of the magnetoresistive effect element in a magnetic playback head.
In the Japanese Unexamined Patent Publication (KOKAI)No. 9-116209, there is language with regard to a structure of a magnetoresistive effect element, and in particular for the purpose of improving the flatness in a recording head, to which purpose one of the first and second magnetic layers is formed within a magnetic field detection region, thereby being no language with regard to technology for solving the problem of a step in the magnetoresistive effect element of a magnetic playback head.
Additionally, in the patent diode disclosure No. 2710210, there is language with regard to a magnetic resistive readout transducer, in which a configuration for minimizing the electrical instability in the junction part between an MR layer and a magnetic bias layer. However, there is no language with regard to technology for solving the problem of a step occurring in a magnetoresistive effect element of a magnetic playback head.
Accordingly, in order to improve on the above-noted drawbacks of the prior art, it is an object of the present invention to provide a compound magnetoresistive effect head and method for manufacturing a compound magnetoresistive effect head that achieves a high recording density.
In order to achieve the above-noted object, the present invention has the following technical constitution.
Specifically, a first aspect of the present invention is a compound magnetoresistive effect head comprising a dedicated playback head comprising opposing first and second magnetic shield films, a magnetoresistive effect element provided between the first and second magnetic shield films and through a first magnetic separation layer and second magnetic separation layer each provided between the first magnetic shield film and the magnetoresistive effect element and between the second magnetic shield film and the magnetoresistive effect element, respectively, and a recording head configured so as to use one of the two opposing magnetic shield films as a first magnetic pole film, and, on a surface of the first magnetic pole film opposite to the magnetoresistive effect element, a coil sandwiched by insulators and a second magnetic pole film, these being laminated thereon, in parallel with the first magnetic pole film, recording being performed by a magnetic field generated in a magnetic gap provided between the first and second magnetic pole films, wherein in the compound magnetoresistive effect head, a ferromagnetic film for stabilizing magnetization of the magnetoresistive effect film and an electrode film for the purpose of causing a current to flow in a magnetoresistive effect film are arranged at both ends of the magnetoresistive effect film, so as to be magnetically and electrically connected thereto, and further wherein the a flattening film being provided between the first and second magnetic separation films in a direction of a height of the magnetoresistive effect element of the playback head.
A second aspect of the present invention is a method for manufacturing a compound magnetoresistive effect head having a dedicated playback head comprising opposing first and second magnetic shield films, a magnetoresistive effect element provided between the first and second magnetic shield films and through a first magnetic separation layer and second magnetic separation layer each provided between the first magnetic shield film and the magnetoresistive effect element and between the second magnetic shield film and the magnetoresistive effect element, respectively; and a recording head configured so as to use one of the two opposing magnetic shield films as a first magnetic pole film, and, on a surface of the first magnetic pole film opposite to the magnetoresistive effect element, a coil sandwiched by insulators and a second magnetic pole film, these being laminated thereon, in parallel with the first magnetic pole film, recording being performed by a magnetic field generated in a magnetic gap provided between the first and second magnetic pole films, wherein in the compound magnetoresistive effect head, a ferromagnetic film for stabilizing magnetization of the magnetoresistive effect film and an electrode film for the purpose of causing a current to flow in a magnetoresistive effect film are arranged at both ends of the magnetoresistive effect film, so as to be magnetically and electrically connected thereto, the method comprising, a first step of forming a first magnetic shield layer, a second step of forming a first magnetic separation layer on the first magnetic shield layer, a third step of forming a magnetoresistive effect film on the first magnetic separation layer, a fourth step of patterning the magnetoresistive effect element film to a prescribed shape, a fifth step of forming a flattening layer having a thickness substantially the same as the magnetoresistive effect element film on the first magnetic separation layer from which the magnetoresistive effect element film is removed, so as to join with the patterned magnetoresistive effect element film, and a sixth step of forming a second magnetic separation layer on the surface of the magnetoresistive effect element film and the flattening film.
By adopting the above-described constitutions, in a compound magnetoresistive effect head formed by lamination of an MR playback head and an ID recording head, and method for manufacturing such a compound magnetoresistive effect head according to the present invention, by flattening a step formed by patterning so as to establish the magnetoresistive effect element height, it is possible to form a thin Al2O3 film between the magnetoresistive effect element and the magnetic shield, thereby achieving a compound head having an MR head with a thin-film playback gap length.